1. Field of the Invention
The present invention relates in general to a process for fabricating lateral bipolar junction transistors (BJT). In particular, the present invention relates to a process for fabricating lateral BJT having improved current gain.
2. Technical Background
Conventional lateral BJT's have limited current gain characteristics due to their inherent limitations in their semiconductor structural configurations. FIG. 1 of the accompanying drawing of the present invention shows schematically the cross section of a conventional lateral BJT, which is employed here for the purpose of description of the present invention.
As is seen in FIG. 1, a conventional BJT is fabricated out of an N-type substrate 1. P-well regions 10, although only one is shown in the drawing, are formed in N-type substrate 1 by methods known in the art. N.sub.+ -type emitter regions 12, as well as N+-type collectors 14 are formed in a P-well 10 subsequently for the bipolar junction transistor. P-well contact regions 16, that is, the contact regions for the base regions are then fabricated thereon. Insulation layer 18 is formed on substrate 1 and metal contacts 20 are then formed.
Since, as is observed in the drawing, emitter region 12 is not sufficiently isolated from the contact region 16 of base region 10, electron flow I, that is, the flow of negative carriers as emitted by emitter region 12, has a great portion thereof being absorbed by contact region 16 of base region 10. The result is the reception of the electron flow I insufficiently large, causing the conventional lateral BJT device to feature a current gain characteristics smaller than expected.